Comparison of changes in etiologic microorganisms causing early-onset neonatal sepsis between preterm labor and preterm premature rupture of membranes

Objective: To investigate changes in the etiologic microorganisms causing early-onset neonatal sepsis (EONS) in preterm labor (PTL) or preterm premature rupture of membranes (pPROM) cases over the past 16 years and to analyze the associated factors. Methods: We included consecutive singleton pregnancies delivered before 34 weeks due to PTL or pPROM. The etiologic microorganisms causing EONS in PTL and pPROM cases were compared between period 1 (1996-2004) and period 2 (2005-2012). Results: There was no difference in the incidence of Gram-positive bacteria causing EONS between period 1 and 2, either in PTL (2.0% versus 2.1%, p = 1.0) or in pPROM (1.5% versus 1.6%, p = 1.0). However, the incidence of EONS caused by Gram-negative bacteria was significantly increased in pPROM (0.6% versus 2.7%, p = 0.040) during period 2, compared to period 1; but not in PTL (0.3% versus 1.2%, p = 0.211). Multivariable analysis revealed that a prolonged ROM-to-delivery interval (>7 d) was significantly associated with EONS caused by Gram-negative bacteria in pPROM (odds ratio: 6.6, 95% confidence interval: 1.4-31.8, p = 0.018). Conclusions: The etiologic microorganisms causing EONS have changed over the past 16 years in pPROM cases but not in PTL cases.